A stage of the Upper Cambrian, underlain by the Maentwrogian and dated at 492.5–488.3 Ma ago (Int. Commission on Stratigraphy, 2004), preceded by the Festiniogian and followed by the Tremadocian.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。